Hello, im trying to do my math homework that involves me using the shell and disk method. I am struggling a bit on it because im confused as to whether I should use Y or X for my equations given a certain rotation around the Y or X axis (or any parallel axis to those two).

It really suck when i wrote down all the notes and just missing that chunk that screws me up. (Angry)

If you want example I can give you some.
Say im trying to label the inner and outer radius(of the two graphs making the space that i am finding the volume on), if the axis im rotating it around is parallel to the x axis, do i use x or y for my equation to the inner/outer radius? What do i use if im rotating around an axis parallel to Y axis? (disk method)

For shell method, im trying to obtain the radius and the height, and the question is pretty much the same as above.